One of the most important Palaeogene reservoirs in Bohai Bay Basin is of the hybrid lacustrine carbonates and clastics

with frequent facies changes and strong heterogeneities.In order to gain a good insight into the distribution of such reservoirs

Q oilfield in Shijiutuo uplift

Bozhong depression

had been analyzed as an example.Based on core

logging and geophysical data

combined with the analysis on the regional tectonic setting

sediment supply

paleogeomorphological and paleoclimatic data

we studied the petrologic characteristics

sedimentary facies as well as the depositional models of the 2

nd

member of Shahejie Formation in Q oilfield.According to this study

the bulk of the 2

nd

member of Shahejie Fm of Q oilfield was developed in a depositional setting favorable for the accumulation of hybrid lacustrine carbonate-clastic deposits.Two depositional models

namely the hybrid-deposit model and the skirt-rim model

were proposed.Uncertainty and risk of reservoir connectivity exist in both models

thus corresponding measures should be taken to lower risk during oilfield development.Hybrid-deposition played a positive role in improving the quality of the middle-deep clasitic reservoir.